High speed piston compressor



Nov. 21, 1933. R. MEYER 1,935,856

- HIGH SPEED PISTON COMPRESSOR Filed Sept. 28,1951

V IIIIIIIIIIIII Patented Nov. 2 1,- 1933 UNITED STATES PATENT OFFICE HIGH SPEED PISTON COMPRESSOR v Robert Meyer, Mulheim-on-the-Ruhr, Germany, assignor to Fried. Krupp Aktiengesellschaft, Essen-on-the-Ruhr, Germany Application September 28, 1931, Serial No. 565,688, and in Germany Deeember'24, 1930 7 10 Claims. (01.230-200) This invention relates to high speed, single acting piston compressors, in which the air drawn in flows to the compression chamber through suction ports provided inthe wall of the cylinder, and in which pistons, provided with piston bolts are used, the open jackets of which face the crank case.

The object of the invention is to eliminate the defects peculiar to this type of compressor by fundamental improvements in the construction of both the piston and the cylinder, and also to enable the weight of the piston to be reduced by this means and, finally, to eliminate heating of the oil circulating in the compressor.

consideration is composed substantially of three cooperating parts: the working piston for providing and compressing the air, the central por tion of the piston with the piston pin bearing, and the separating piston or crosshead. The lastmentioned piston or crosshead serves to prevent any communication between the suction ports and the interior of the crank casing for all positions of the piston, because otherwise the oil from the crank casing passes over the working piston which is open at one side, into the suction chamber. In compressors with primary admission valves the outer edge of the working piston exposes the suction ports wholly or partially for the purpose of obtaining thenecessary filling of the cylinder. This necessity is done away with in compressors, in which suction valves arev placed in the piston. The working piston and the separating piston are of the same diameter and as guide the piston in the bore of the cylinder.

' The type of construction described has the following fundamental disadvantages.

Owing to the position of the separating piston being dependent on the arrangement of the suction ports the minimum length of the piston system is determined by this dependency. v The piston is consequently of necessity both long and heavy.

The separation of the chambers mentioned makes it necessary to keep the diameter of the separating piston equal to that of the diameter of the cyinder. Furthermore, the provision of a sufficiently longguide which shall be but slightly subjected to wear and be free from deviation and which will act as a reliable packing for this part of the piston is very greatly limited with this old design, as the very great increase in weight which arises owing to the comparatively great diameter of the separating piston causes The piston in the type of compressor under ing apparatus isnecessary.

a dangerous increase time driving efl'ec't oi in- .ertia. If a vacuum be created in the suction chamber, for example when regulating with the suction branch shut oil, the loss of oil particularly in cylinders of largediameter exceeds the permissible limit. on the other hand if the 00 chamber is under the pressure of the previous stage in the case of multistage compression, the packing of the separating piston and the crank casing chamber becomes specially diflicult.

Furthermore, in the old design of piston compressor the heat radiated from the working piston is transmitted almost undiminished to the separating piston through large accumulations of material .and above all by the large valve coupling members. By thecentrifugal action of the crank drive the oil in the crank casing is heated gradually by the heating action of the large and hot surface of the piston. The oil is rendered thin, and losses by leakage, wear and consumption of power result. Therefore. in continuously working compressors, particularly in the case of stationary compressors, a special oil cool- Furthermore whereas during the suction stroke the cold air admitted comes into contact 30 with only a small surface area of the hot mass of the piston, the supply of cold air ceases on the compression stroke as in this-case the formation a of a vacuum does not take place. There is merely a shifting of the volume of enclosed between the two pistons, which air, during the compression stroke, is heated up bythe working piston and passes over into-the working cylinder at the commencement of the suction stroke.

By the design of compressor according to the present invention not only the defects above described are eliminated, but a much more advantageous and improved type of compressor is attained.

The invention is based upon the idea that the separating piston or crosshead can be removed from the bore of the working cylinder, without interfering with its function oi separating the crank casing chamber from the suction chamber and that the piston can be located in a cylinder of small diameter connected with the working cylinder. In carrying out this idea the separating piston is constructed as a complete trunk piston or cross head and the main portion of the guiding of the piston system transferred to it. This removal of the separating piston from the working cylinder completely does away with the dependence of the position of the separating piston on the arrangement of the suction ports which has hitherto been the predominant factor in hindering the improvement of the type of compressor under consideration. The reduced surface area of the piston thus attained is the cause of a supply of cold air to the interior of the piston of a volume hitherto not attained in this type of compressor and, in addition to this, this reduction of surface area gives a better thermal effect. The constructional advantage of a reduction in the length of the piston and above all in the weight thereof, is important. Finally, the new technical effect of an elimination of the danger of the oil being heated is obtained by the improvements according to the invention.

An embodiment of the invention is shown by way of example in the accompanying drawing which diagrammatically illustrate the parts under consideration of a piston compressor designed in accordance with the invention, and in which Fig. 1 is asection, taken through the longitudi nal axis of the piston pin in the position the piston occupies at the beginning of the suction stroke,

Fig. 2 shows the piston in the position at the end of the suction stroke, the section being taken at right angles to the center line of the piston pin, and

Fig. 3 is a sectional view of a compressor, with certain parts in elevation, which embodies my novel piston assembly.

Referring to the drawing, a denotes the working cylinder which is connected to a cylinder b. the internal diameter of which is kept as small as possible. The separating piston or crosshead e which divides the crank case chamber 0 from the suction chamber d runs in the cylinder b and is constructed as a complete trunk piston closed at one end and carrying a piston pin bearing 1 and suitable packing rings. Its open end faces the crank case 0. The head of the separating piston e carries a system of very thin ribs 0 of any de-- sired form, for example flat ribs, which act both as supports for the working piston h and the suction valve (not shown in the drawing) placed in the chamber i and also act for cooling purposes. These ribs 9 do not project laterally at any point beyond the head of the piston e so that they can enter thecylinder b. The skirt k of the working piston is only of suchlength as is necessary to lodge the piston rings needed for packing purposes. In order to obtain a smooth external surface at the head of the piston skirt is may conveniently extend on the side of the base It turned toward the suction chamber d, so-that the working piston has the shape of a flat pot which covers the separating piston e like a cap. The

admission of the air drawn in tothe cylinder a takes place in the embodiment shown through a narrow annular passage 1. 7

The fact that the separating piston is not used for controlling the air inlet ports makes it possible as a further development of the design according to the invention,to bring the packing m which is independent of the bore of thecylinder -a so far forward into the latter as the stroke n of the piston permits making an allowance for a small stroke clearance 0 (Fig. 2) The total length of the piston is thus considerably shortened, and

the piston is much lighter than it is in the ordipiston e from the arrangement of the suction ports thus obtained enables in compressors with full action suction valves the additional advantage that the cooling jacket r may be made relatively long as the suction port can always be arranged behind the cooling jacket (Fig. 1).

4 When the working piston is constructed as a single thin disc and the pot shape dispensed with,

' various cooling ribs 9 and into the suction valve.

As the power of resistance possessed by a system of ribs enables the provision of very thin ribs and as, on the other hand the very large surfaces of the ribs are exposed on both sides to the current of cold air and as, finally, the small amount of the material of which the ribs are composed permits of only small amounts of heat being stored up, the amount of heat carried away from the base h of the piston is very considerable. The first cooling is considerably increased by the fact that at the beginning of the compression stroke (Fig. 2) a repeated cooling of the ribs takes place, because, in contradistinction to the known type of construction, cold air is drawn in for this part of the stroke also by the action of the vacuum which is created. The cold air which therefore flows in continuously increases the withdrawal of heat very greatly. The bases of the ribs projecting from the base of the separating piston therefore remain cool and consequently also the piston e separated by the ribs from the working piston h. In this way the new technical effect is secured with the simplest of means, that the heat radiated from the working piston is carried off before it passes over to the separating piston. Furthermore, if instead of flat straight or curved ribs perforated .or grid-like cooling walls be used, a further increase in the cooling may be obtained. The oilwhich remains cool retains its lubricating power unimpaired, losses by leakage, wear and tear and consumption of power are less and any oil cooling apparatus particularly for stationary compressors, is rendered superfluous. The greatly reduced diameter of the separating piston affords per se a reduction of leakage. As furthermore packing rings can be used in adequate numbers without materially increasing the weight a packing which will resist compressed air can be obtained without difflculty.

The invention permits of the use of suction valves of any desired form as both the reliable support thereof and their anchoring and also suitable formation of the cooling ribs is ensured 185 Finally the invention can be applied der of smaller diameter than said working cylinder intermediate the latter and said crankissaaso case, a crosshead in the form of a separating trunk piston in said guiding cylinder, and a connector between said piston and crosshead.

2. The combination in a piston compressor, of a crank-case therefor, a working cylinder, a working piston in said cylinder, a guiding cylinder of smaller diameter than said working cylinder intermediate the latter and said crank-case, a crosshead in the form of a separating trunk piston in said guiding cylinder, and thin walled connecting means intermediate said piston and crosshead adapted to prevent any substantial passage of heat from said working piston to said crosshead. v

3. The combination in a piston compressor, of a crank-case therefor, a working cylinder, a working piston in said cylinder, a guiding cylinder of smaller diameter than said working cylinder intermediate the latter and said crank-case, a crosshead in the form of a separating trunk piston in said guiding cylinder, and thin walled connecting means intermediate said piston and crosshead adapted to prevent any substantial passage of heat from said working piston to said crosshead, said guiding cylinder being of substantial length to guide said crosshead and said working piston in their respective cylinders.

4. The combination in a piston compressor, of a crank-case therefor, a working cylinder, 9. diskshaped working piston in said cylinder, a guiding cylinder of smaller diameter than said working cylinder intermediate the latter and said crankcase, said guiding cylinder extending within said working cylinder so far as to leave a maximum distance between the inner extremity of said auxiliary cylinder and inner surface of the working piston disk equivalent to the length of the stroke of said "working piston plus a slight clearance space, a crosshead in the form of a sepa-' rating trunk piston in said guiding cylinder, and thin walled connecting means intermediate said piston and crosshead adapted to prevent any substantial passage of heat from said working piston to said crosshead, said guiding cylinder being of substantial length to guide said crosshead and said working piston in their respective cylinders.

5. The combination in a piston compressor, of

I a crank-case therefor, a. working cylinder, a diskshaped working piston .in said cylinder, valve seating means disposed upon the end of said disk facing the end of said cylinder, said cylinder end and working piston defining the extremities of 'a compression chamber, a guiding cylinder of smaller diameter than said working cylinder intermediate the latter and said crank-case, a crosshead in the form-or a separating trunk piston in said guiding cylinder, thin walled con necting means intermediate said piston and crosshead adapted to prevent any substantial passage of heat from said working piston to said crosshead, and a suction chamber surrounding said guiding cylinder, crosshead and connecting means at the end of said working piston opposite said compression chamber.

6. The combination in a piston compressor, of

a crank-case therefor, a working cylinder, a disk-shaped working piston in said cylinder,

; valve seating means disposed upon the end of said disk facing the end of said cylinder, said cylinder end and working piston defining the extremities of a compression chamber, a guiding cylinder of smaller diameter than said working cylinder intermediate the latter and said crankcase, a crosshead in the iorm of a separating trunk piston in said guiding cylinder, thin walled connecting means intermediate said piston and crosshead adapted to prevent any substantial passage of heat from said working piston to said crosshead, an annular suction chamber surrounding said guiding cylinder, crosshead and connecting means at the end of said working piston opposite said compression chamber rand an inlet port for said suction chamber.

7. The combination in a pistoncompressor, of

a crank-case therefor, a working cylinder, a diskshaped working piston in said cylinder, valve seating means disposed upon the end of said disk facing the end of said cylinder, said cylinder end and working piston defining the extremities of a compression chamber, a guiding cylinder of v smaller diameter than said working cylinder incylinder between said inletport and the head end thereof.

8, The combination claimed in claim 2 wherein said connecting means is confined to a diameter not greater than the diameter of said guiding v cylinder to allow the reciprocation'of said conpecting means within said guiding cylinder.

9. The combination in apiston compressor, of a crank-case therefor, a piston assembly comprising a working piston, a crosshead in the form of a separating piston and a connecting portion intermediate said piston and crosshead, a working cylinder for said working piston, a second cylinder of smaller diameter for said crosshead extending within saidworking cylinder, said piston assembly adapted to be driven by a mechanism in said crank-case, a space surrounding said crosshead and second cylinder forming a suction chamber for said working cylinder with said crosshead constituting a closure between said suction chamber and said crank-case.

10. The combination claimed in claim 9 wherein said connecting'portion comprises thin walled connecting elements disposed in said suction chamber. 7 a

noaaa'r MEYER. 

